The purpose of this research is to establish the cellular events that follow the cell-mediated antigenic stimulation of immunocompetent cells, the mechanism of antigenic stimulaton, and the genesis of differential effector lymphocytes from undifferentiated precursors. The mechanism by which proliferation and differentiation are regulated, and the relation between cells synthesizing antibody and the cells differentiating into cytotoxic effector lymphocytes will be studied. The research will utilize an in vitro culture system in which a primary cell-mediated immune response comparable to that seen in vivo can be obtained, and Cr51 release assay for the enumeration of effector lymphocytes. Cell separation procedures will be utilized for concentrating and separating various cell components involved in this response.